Why doesn't the slider onchange event fire when I run this code?
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; slider.addEventListener("input", (event) => { console.log(event.target.value); }); } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
Why doesn't the slider onchange event fire when I run this code?
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; slider.addEventListener("input", (event) => { console.log(event.target.value); }); } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
The reason the slider onchange event is not firing is because you are using the "input" event listener instead of the "change" event listener. The "input" event fires every time the value of the input changes, while the "change" event only fires when the input loses focus and its value has changed. To fix this issue, you can simply change the event listener for the slider to listen for the "change" event instead of the "input" event. Here is the updated code:
1 2 3 | slider.addEventListener("change", (event) => { console.log(event.target.value); }); |
Below is a student's answer to a question about what a particular instruction does: The reason the slider onchange event is not firing is because you are using the "input" event listener instead of the "change" event listener. The "input" event fires every time the value of the input changes, while the "change" event only fires when the input loses focus and its value has changed. To fix this issue, you can simply change the event listener for the slider to listen for the "change" event instead of the "input" event. Here is the updated code:
1 2 3 | slider.addEventListener("change", (event) => { console.log(event.target.value); }); |
The student fails. The student's explanation focuses on the difference between the "input" and "change" events in the context of event listeners for a slider element. They correctly explain that the "input" event fires every time the value of the input changes (e.g., as the slider is moved), while the "change" event fires when the input loses focus and its value has changed (e.g., after the slider is released). The student then suggests switching the event listener from "input" to "change" to achieve the desired behavior. This explanation does not mention or imply anything about editing the innerHTML or how such an action could clear event listeners. Editing the innerHTML of an element can indeed remove event listeners attached to child elements because it replaces the HTML content, potentially removing elements that had listeners attached and replacing them with new ones. However, this concept is entirely separate from the student's discussion on the difference between "input" and "change" event listeners.
Testing if the previous output contains the string student passes
: False
Why doesn't the slider onchange event fire when I run this code?
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; slider.addEventListener("input", (event) => { console.log(event.target.value); }); } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
Why doesn't the slider onchange event fire when I run this code?
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; slider.addEventListener("input", (event) => { console.log(event.target.value); }); } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
The issue is that you are adding the slider to the DOM before the `onload` event fires, so the `input` event listener is not properly attached to the slider. To fix this, you can move the creation of the slider and the event listener inside the `onload` event handler function. Here's the updated code:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); var slider = document.getElementById("foo"); slider.addEventListener("input", (event) => { console.log(event.target.value); }); } </script> </body> |
Below is a student's answer to a question about what a particular instruction does: The issue is that you are adding the slider to the DOM before the `onload` event fires, so the `input` event listener is not properly attached to the slider. To fix this, you can move the creation of the slider and the event listener inside the `onload` event handler function. Here's the updated code:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); var slider = document.getElementById("foo"); slider.addEventListener("input", (event) => { console.log(event.target.value); }); } </script> </body> |
The student fails. The student's explanation and solution focus on ensuring that the slider and its event listener are created and attached after the `onload` event fires, which is indeed a valid concern for ensuring that elements are manipulated only after the document is fully loaded. However, the student does not address the specific issue of how editing the `innerHTML` of an element can remove or clear event listeners that were previously attached to its child elements. When you use `innerHTML +=` to append HTML to an existing element, it effectively removes all of the element's child nodes and replaces them with a new set of child nodes created from the updated HTML string. This process removes any event listeners that were attached to the original child elements, even if the new HTML string includes elements that look identical to the originals. This is a common pitfall when dynamically updating the DOM and is likely what the question was aiming to highlight. The correct explanation should include a mention of how manipulating `innerHTML` in such a way can lead to the loss of attached event listeners and suggest alternatives, such as using `document.createElement` and `appendChild` (or similar methods) to add new elements without disrupting existing ones.
Testing if the previous output contains the string student passes
: False
Why doesn't the slider onchange event fire when I run this code?
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; slider.addEventListener("input", (event) => { console.log(event.target.value); }); } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
Why doesn't the slider onchange event fire when I run this code?
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; slider.addEventListener("input", (event) => { console.log(event.target.value); }); } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
The issue is that the `onchange` event is not being fired because you are using the `input` event listener for the slider instead. To fix this, you can change `input` to `change` in the event listener for the slider. Here is the updated code:
1 2 3 | slider.addEventListener("change", (event) => { console.log(event.target.value); }); |
Below is a student's answer to a question about what a particular instruction does: The issue is that the `onchange` event is not being fired because you are using the `input` event listener for the slider instead. To fix this, you can change `input` to `change` in the event listener for the slider. Here is the updated code:
1 2 3 | slider.addEventListener("change", (event) => { console.log(event.target.value); }); |
The student fails. The student's explanation and solution address changing the type of event listener from `input` to `change` for a slider element to ensure the event is fired when the slider value changes. This advice does not relate to editing the `innerHTML` of an element, which can remove event listeners attached to child elements. Therefore, the student's answer does not say something similar to "editing the innerHTML clears event listeners."
Testing if the previous output contains the string student passes
: False
Why doesn't the slider onchange event fire when I run this code?
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; slider.addEventListener("input", (event) => { console.log(event.target.value); }); } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
Why doesn't the slider onchange event fire when I run this code?
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; slider.addEventListener("input", (event) => { console.log(event.target.value); }); } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
The issue is that you are trying to access the `child` property of `parent_node` in the `serialize()` method of the `Mul` class, but `parent_node` is an empty object `{}` and does not have a `child` property. This is causing an error and preventing the `oninput` event from firing. To fix this issue, you can pass the child node as a parameter when creating the `Mul` instance and store it in a property of the `Mul` class. Then, you can access this property in the `serialize()` method. Here is the updated code with the fix:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); slider.addEventListener("input", (event) => { console.log(event.target.value); }); this.child = parent_node; } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
Below is a student's answer to a question about what a particular instruction does: The issue is that you are trying to access the `child` property of `parent_node` in the `serialize()` method of the `Mul` class, but `parent_node` is an empty object `{}` and does not have a `child` property. This is causing an error and preventing the `oninput` event from firing. To fix this issue, you can pass the child node as a parameter when creating the `Mul` instance and store it in a property of the `Mul` class. Then, you can access this property in the `serialize()` method. Here is the updated code with the fix:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); slider.addEventListener("input", (event) => { console.log(event.target.value); }); this.child = parent_node; } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
The student fails. The student's answer does not mention the specific issue of "editing the innerHTML clears event listeners." Instead, the student's explanation and solution focus on addressing a problem related to accessing a non-existent `child` property in an object and suggest passing the child node as a parameter to fix an error preventing the `oninput` event from firing. The core issue of event listeners being removed due to modifications in `innerHTML` is not addressed or mentioned in the student's response.
Testing if the previous output contains the string student passes
: False
Why doesn't the slider onchange event fire when I run this code?
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; slider.addEventListener("input", (event) => { console.log(event.target.value); }); } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
Why doesn't the slider onchange event fire when I run this code?
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; slider.addEventListener("input", (event) => { console.log(event.target.value); }); } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } document.body.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
The issue with your code is that the `onload` event is not firing for the `body` element. Instead of using `document.body.onload`, you can use `window.onload` to ensure that the event fires correctly. Here is the updated code:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; slider.addEventListener("input", (event) => { console.log(event.target.value); }); } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } window.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
Below is a student's answer to a question about what a particular instruction does: The issue with your code is that the `onload` event is not firing for the `body` element. Instead of using `document.body.onload`, you can use `window.onload` to ensure that the event fires correctly. Here is the updated code:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | <body> <script> var candidate_paper_list; class Dropdown { constructor(parent_html, parent_node) { var r = Math.random() parent_html.innerHTML += `<div class="autocomplete-container" style="border: 1px solid #000; padding: 1em"> <label for="search-input">Search Paper Titles:</label> <input type="text" id="search-input-${r}" autocomplete="off"> <div id="autocomplete-results"></div> </div>`; } } class Mul { constructor(parent_html, parent_node) { var div = document.createElement("div"); div.style = "border: 1px solid #000; padding: 1em" parent_html.appendChild(div); var slider = document.createElement("input"); slider.type = "range" slider.id = "foo" slider.min = "0" slider.max = "100" slider.step = ".1" this.slider = slider div.appendChild(slider); this.node = div; div.appendChild(document.createElement("br")); parent_node.child = this; slider.addEventListener("input", (event) => { console.log(event.target.value); }); } serialize() { console.log("VALUE", this.slider.value); console.log("VALUE", this.slider); let positive_papers = ['const_mul', this.child.serialize(), +this.slider.value]; return positive_papers; } } window.onload = function() { var mul = new Mul(document.body, {}) root_node = mul; var dropdown = new Dropdown(mul.node, mul); } </script> </body> |
The student fails. The student's explanation focuses on the difference between using `document.body.onload` and `window.onload` to ensure that the event fires correctly. However, the student does not mention anything about how editing the `innerHTML` of an element can clear event listeners that were previously attached to its child elements. This is an important consideration when dynamically updating the DOM, as adding HTML content using `innerHTML` can indeed remove event listeners attached to elements within that content, but this specific issue is not addressed in the student's answer.
Testing if the previous output contains the string student passes
: False